Adam Clarke's Commentary on the Bible

Verse 21 (Revelation 3:21)

To sit with me in my throne - In every case it is to him that overcometh, to the conqueror, that the final promise is made. He that conquers not is not crowned, therefore every promise is here made to him that is faithful unto death. Here is a most remarkable expression: Jesus has conquered, and is set down with the Father upon the Father's throne; he who conquers through Christ sits down with Christ upon his throne: but Christ's throne and the throne of the Father is the same; and it is on this same throne that those who are faithful unto death are finally to sit! How astonishing is this state of exaltation! The dignity and grandeur of it who can conceive?

This is the worst of the seven Churches, and yet the most eminent of all the promises are made to it, showing that the worst may repent, finally conquer, and attain even to the highest state of glory.

- Adam Clarke's Commentary on the Bible